Patent GB-976374-A (GB)
Title: Improvements relating to laminates
Inventor: SIMPSON TERENCE EDWARD
IPC: B32B15/08
Filed: 1962-09-06
Abstract: 976,374. Laminates. FORMICA INTERNATIONAL Ltd. Oct. 21, 1963 [Sept. 6, 1962], No. 34222/62. Heading B5N. [Also in Division B8] A laminate suitable for use as, e.g. labels, comprises a base layer having superimposed on one or both sides: (a) a coloured layer comprising a melamine resin; (b) a colourless transparent layer also comprising a melamine resin; and (c) a layer of etchable metal such as copper or aluminium, bonded to layer (b) by an adhesive preferably comprising a polyvinyl acetal, such as polyvinyl butyral and a phenolic resin such as phenol formaldehyde. When the upper surface of the base layer is coloured, layer (a) may be omitted. Suitable melamine resins are those formed from melamine and an aldehyde, usually formaldehyde, with or without e.g. urea. The base may comprise ceramics, metal, glass, stone, wood, leather, paper, cloth or one or more layers of inorganic or organic, coloured or colourless, woven, unwoven or knitted fibrous fillers, e.g. of glass, asbestos, cotton or other vegetable fibres, regenerated cellulose, cellulose derivatives or a synthetic material, impregnated with a phenolic or other thermosetting resin. Alternatively, the base may comprise softenable fibres which are rendered cohesive on heating or under the action of a solvent. Optionally, pigments and/or particulate or granular fillers may be included in the base. Coloured layer (a) incorporates inorganic pigments or organic dyestuffs, in which latter case the dyestuff may be dissolved or dispersed in the resin or adsorbed on a colourless filler of the types mentioned above. The resin content of this layer is less than 45%, whilst that of layer (b), which may comprise resin-impregnated or coated paper or other fibrous material is at least 60%. In forming the laminate, preformed layers may be assembled and subjected to heat and pressure; alternatively the forming may be in two or three stages whereby the base and layer (a) are first united under heat and pressure, and then layer (b) is applied to ( a) either in sheet form or by coating and united thereto by further heat and pressure, layer (c) being applied at the same or a subsequent stage. With either method, the resin in layer (b) should be partially pre-cured. Optionally, an adhesive layer may be used to bond layer (a) to the base. To produce design-bearing labels, acid etching may be used which removes the metal locally, followed by sand-blasting to remove adhesive in exposed areas and burnish the remaining parts of the metal. In examples: (1) the base comprises ten phenol-formaldehyde impregnated Kraft paper sheets, resin content 32%; layer (a) comprises a sheet of red-pigmented, titanium dioxide-loaded paper impregnated with melamine-formaldehyde resin (resin content 40%); layer (b) comprises a sheet of alpha-cellulose impregnated with a melamine resin (resin content 66%) and layer (c) comprises copper foil adhered to (b) by a mixture comprising equal parts phenol-formaldehyde and polyvinyl butyral resins. The layers are assembled and lamination occurs at 1500 p.s.i. and 150‹ C. (ii) A base and layer (a) as in (i) are united at 1500 p.s.i. and 150‹ C. and then remaining layers as in (i) are applied and the whole subjected to similar heat and pressure.